Performance of Cr-Al coating on carbon steel to control high temperature corrosion due to ash deposit

A common problem found during burning fuels containing vanadium, sodium and sulfur is the high temperature corrosion attack on metallic components of a combustion system. This phenomenon is of special interest due the increased use of heavy oil with a high content of vanadium and sulfur. This research describes the development of corrosion resistant metallic coating on carbon steel based on chromium-aluminum. Diffusion coating by pack cementation was the technique used to applied this coating. The optimization of the coating was performed. Then, coated and uncoated samples were exposed in laboratory test to Na2SO4/V2O5 fused salt in SO2/SO3/O2 atmospheres at 700 C. Results of this experimental program showed that the Cr-Al coating tested adequately protected the base metal of the corrosion attack. Thickness losses on coated carbon steel were up to five times lower than on 5% Cr steel. The work done demonstrated that the Cr-Al coatings can be used to control corrosion due to fused salts, under the tested conditions